Michael Dunn returns to his seat after reading his statement, which included an apology to the Davis family, during his sentencing hearing.
Photograph: Bruce Lipsky/AP

The man convicted of shooting dead a Florida teenager in a dispute over loud rap music has been given the maximum possible sentence of life in prison without parole plus 90 years.

Michael Dunn’s sentence was handed down after Lucia McBath, mother of 17-year-old Jordan Davis, broke down in the courtroom on Friday, telling her son’s killer through tears that she forgave him.

Dunn, who was convicted of murder earlier this month, sat impassively as McBath spoke of the devastation she felt at losing her only child in the November 2012 shooting at a Jacksonville gas station.

“For years to come I will be forced to celebrate my son’s birthday without his presence. As I quietly watch my friends’ boys grow into young men, I will forever be reminded of what might’ve been for my Jordan,” she said.

“I choose to forgive you Mr Dunn for taking my son’s life. I choose to release the seeds of bitterness and anger and honour my son’s love. I choose to walk in the freedom of knowing God’s justice has been served. I pray that God has mercy on your soul.”

Judge Russell Healey sentenced software engineer Dunn, 47, to maximum prison terms on all counts: life without parole for the first-degree murder of Davis, three consecutive 30-year sentences for the attempted second-degree murder of the teenager’s friends, who were in the car with him, and an additional 15 years for shooting into a moving vehicle.

“Mr Dunn, your life is effectively over,” Healey said. “This tragedy should and could have been prevented.”

At his murder trial that ended on 1 October, Dunn admitted firing 10 shots into the youths’ Dodge Durango during the altercation over loud music blaring from the SUV parked alongside his car. Even though he fired the final shots as the vehicle sped away, he claimed he was acting in self-defence because Davis, he said, had brandished a gun and moved to attack him after refusing to turn the volume down. Police found no weapon and witnesses said they never saw one.

Dunn maintained his innocence during a brief address to the court on Friday, in which he repeated the claim he made at his trial that he felt his life was in danger.

“I want the Davis family to know that I truly regret what happened,” said Dunn, who appeared in handcuffs and wearing a bright orange prison jumpsuit. “I’m sorry for their loss and if I could roll back time and do things differently I would. I was in fear for my life and did what I thought I had to do. Still, I’m mortified I took a life, whether it was justified or not.”

Several jurors who convicted Dunn sat crying in the courtroom at Friday’s sentencing hearing as Ron Davis, the teenager’s father, delivered his own emotional testimony.

“I wish no parent had to cry these kinds of tears,” he said. “I gave him his first kiss as he came into the world. I held my son in my arms in the hospital and kissed him his last goodbye. The old Ron Davis died that very night with Jordan. We all loved him very, very much.”

After the hearing, Davis told reporters that he did not believe Dunn’s courtroom apology, delivered during a 25-second address, was sincere. “It was much too little and much too late,” he said, echoing comments he made earlier in the week that neither Dunn, nor anybody from his family, had approached them in the two years since his son was killed.

McBath was also dismissive. “I didn’t see any remorse, I didn’t see any humility,” she said. “It’s why I feel so saddened for him because he has emptiness inside of him. That’s what he will live with for the rest of his life.”

A jury at Dunn’s February trial convicted him on the attempted murder charges but could not reach a verdict on the murder count, leading to his week-long retrial. Prosecutors told of how Dunn and his fiancee, who had attended his son’s wedding on the day after Thanksgiving, returned to their hotel after the shooting, watched movies, ate pizza and drank wine before making a two and a half hour drive home to Satellite Beach, Florida, the following morning without alerting authorities.

Before passing sentence, Healey rejected a motion from Dunn’s lawyers seeking a new trial. They had cited what they saw as improper rulings by the judge, including his decision to allow testimony about gunshot trajectory and that he dismissed one juror without evidence of misconduct.

They also claimed Dunn was denied a fair trial by the judge’s denial of their request to move proceedings away from Jacksonville.